[Dogg]

Since you have to remove drywall, you can use this opportunity to run you speaker wires in the wall. I would also wall-mount the rear speakers. This will allow you to change/upgrade whenever the need/urge arrises. Some speakers come with mounting kits or you could use shelves. Either way, the speaker wire is mostly unnoticable as only a few inches is visible.

Building in-wall speakers would be a matter of trial and error and it would be a completely custom job. You will basically be building speakers from scratch in the wall. Just putting a single speaker in the wall won't sound very good.